High-quality shallow, intermediate and deep shocks from the Southern Tyrrhenian area (interval: 1985-1995) are analysed to draw inferences on the complex shape of the underlying Benioff zone. The hypothesis of an active NW-oriented subduction of the lithosphere, generated and stressed by the opening of the Tyrrhenian basin, is confirmed. The fractal behaviour of seismic data in its five-dimensional set (magnitude, time and space) is significantly identified, even if within specific ranges. The light but significant variations of the different fractal dimensions measured during more recent years is explained in terms of a reduction in the fracturing degree of the Southern Tyrrhenian crust.